There are numerous devices disclosed in the prior art for automatically closing doors, especially sliding doors. All of these devices, however, suffer from one drawback or another.
Many prior art references, such as U.S. Pat. No. 5,251,402 to Richardson et al., U.S. Pat. No. 5,285,596 to Kinsey, and U.S. Pat. No. 5,131,188 to Hutchison et al., disclose self-contained automatic door closure mechanisms that are either built into the wall of the building or the door-frame of the sliding glass door. These devices are of little value, obviously, to property owners having sliding glass doors that were not equipped with these self-contained door closure mechanisms when originally installed. These self-contained door closure mechanisms are also undesirable due to their high cost and the extreme difficulty involved in repairing or replacing these devices.
Other prior art references, such as U.S. Pat. No. 5,313,739 to Nelson et al. and U.S. Pat. No. 4,471,575 to Stout, disclose externally mounted mechanisms for automatically closing sliding doors. These devices, however, also have several drawbacks. First, these devices are mounted on the outer surface of the sliding door and near its top edge, rather than lying within the flat plane of the sliding track, and therefore distract from the overall streamlined appearance of the sliding door. These devices also require mounting plates and screws that damage any finished wood trim around the door frame. Furthermore, these devices employ one or more elongated helical springs that are stretched when the door is opened and then contract to close the door. Over time, the center sections of the elongated helical springs will experience mechanical stress that causes the springs to slacken and lose their resiliency. Lastly, these devices also have an inordinately large number of moving parts and are of a generally "flimsy" design.
There is therefore a need for an automatic door closure mechanism for sliding glass doors that may be quickly and easily attached to the exterior of sliding glass doors.
There is also a need of an automatic sliding door closure mechanism that can be mounted within the plane of the sliding track so as not to affect the outline or contours of the sliding door.
There is a still further need for a sliding glass door closure device which is of a relatively sturdy construction and which does not use elongated helical springs that slacken and lose resiliency under repeated mechanical stress.